Blow Mold Tool with Retractable Base Portion

ABSTRACT

Blow molding tools and a method of blow molding which provide that the tool have a retractable push up section in the base which allows for the article molded by the tool to have a recessed base internal to an otherwise hollow structure. As the push up is moveable, adjustment of the push up portion can be performed during an automated blow molding operation so as to allow release of the blow molded article.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of U.S. patent application Ser. No.13/340,263, filed Dec. 29, 2011, and currently pending, which is in turna Continuation-in-Part (CIP) of U.S. Utility patent application Ser. No.13/087,883, filed Apr. 15, 2011. The entire disclosure of both the abovedocuments is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

This disclosure relates to the field of blow mold tooling for use inblow molded plastics, particularly to a blow mold tool including amoveable component which allows for the blow molding of a container witha deeply indented base.

2. Description of the Related Art

Because of the various competing desires in packaging, a large number ofproducts are changing from being packaged in glass or metal to beingpackaged in plastics. Plastics are generally lighter and more resilientthan other packing alternatives, and can be recycled. There are also awide variety of plastics available which can be selected depending onproperties desired to properly hold the products sold in the container.The most common type of plastic containers are probably polyethyleneterephthalate (PET) containers which can be blow molded and can providefor a clear finish in the final product which resembles glass.

It is generally well established that it is almost always less expensiveto store products packaged in plastic containers in a taller verticalspace than over a greater horizontal space. Storing items in avertically efficient manner means that more items can be stored on asmaller surface area—i.e., less space is needed to store items in awarehouse or retail location. Further, when stacked vertically, itemscan be transported more efficiently on a smaller surface area resultingin fewer trips. Thus, the ability to easily and stably stack containersis very important and in most storage and transport scenarios, there arealways a number of containers of the same size and shape stacked on topof each other.

The stacking of plastic containers, however, is often much morecomplicated than the placement of one container on top of anothercontainer. Most plastic containers provide for an extended neck which istaller than the main body of the container structure. This neck allowsfor a lid to easily be screwed, snapped, connected or otherwisepositioned on and off. At the same time, however, when containers arestacked, generally the higher container in the stack will rest on thelower container's lid or neck due to this vertical extension. When thishappens, the weight of that upper container is only distributed acrossthe lid of the lower container (or the rim of the neck if the containeris empty). Thus, the weight of the upper container is displaced on asmaller surface area comprised of just the lid (or neck) of the lowercontainer. In this unstable orientation, the shoulder between the neckand the top surface of the container bears significant weight from thestack.

In some cases, the neck is simply unable to bear the necessary weight ofthe stacked containers above it. For example, in narrow neckedcontainers, the lid or rim is so small when compared to the base of theupper container that the stack is unstable; i.e., the surface area ofthe base of the higher container is so large that it cannot be supportedin a balanced manner by the lid of the lower container, which has a muchsmaller surface area. Thus, the stacking of these types of containers isgenerally not possible without supplemental support. One common practiceis to place a cardboard or other sheet or support around the necks andbetween the rims of supporting containers in a stack in order todistribute the force of the containers resting above. Because of theproblems inherent to stacking these types of containers, the containersare often distributed in packing boxes which only hold a single layer ofcontainers, but can themselves be stacked, or with sheets of cardboardor another segregating material between the layers of the stack toprovide for force distribution.

Even in container designs with wider necks, and thus broader surfaceareas for stacking, segregating sheets between layers of the stack areoften still necessary to prevent the mass of the above containers frombeing focused too narrowly on the shoulder of the lower container,resulting in overall instability in the stacked container structure andpossible malformation of the lower mass-bearing containers in the stack.Thus, even when these wider necked containers have traditionally beenstacked for storage or transport, supports are utilized. For example,generally these wider neck containers are positioned to form a firstlayer. This first layer then has a piece of segregation material placedon it (usually a cardboard sheet), and a second layer is placed on thesegregation layer. This process of sandwiching supplemental supportsbetween the layers of containers in the stack is repeated until adesired stack height is obtained. Because of the use of the supplementalsupports, stacks in these arrangements could result in containers at thesecond layer being positioned directly over containers in the firstlayer, or could result in offsets in the containers between the stacksto further distribute force.

While this form of transport and storage is effective, it has numerousinherent problems. First, this method tends to result in the productionof a lot of excess packing material (used as segregation sheets andsupports) which are discarded by the end user of the containers. Theproblem can exist at possibly three different points. The problem existsfirst when empty containers are stacked and shipped from the packagingmanufacturing plant to the plant where they are to be filled. Theproblem exists again when the containers are filled and shipped to endretailers. The problem can also exist in the transport of usedcontainers to a recycling or refilling facility. Thus, there is apossibility that segregation supports are created and discarded threetimes for the same load of containers. Second, this method results inexcess costs and a loss in efficiency in the moving and storage ofcontainers. The necessary supplemental supports add to the cost ofstoring and transporting the containers. Further, stacking thecontainers in this manner with supplemental supports can complicate thestacking and storing process.

U.S. patent application Ser. No. 13/087,883, incorporated herein byreference, describes a container which provides for a recessed portionof the base. This portion allows for a the neck of a lower container ina stack to be placed in the recessed portion of the base of the highercontainer, resulting in the bottom of the higher container beinggenerally flush with the top of the lower container. Thislid-within-base orientation among the stacked containers improves thestackability of the containers and, in eliminating the need forsupplemental supports, remedies many of the problems inherent totraditional stacking methodologies (e.g., increased cost, increasedwaste and decrease efficiency).

However while this lid-within-base design provides numerous benefits forthe storage and transportation of containers, currently there areproblems in the art in the manufacturing of these recessed basecontainers.

One problem with the manufacture of these recessed base containers isthat it is generally hard, if not impossible, to form the legs of thecontainer around the recessed base. In a traditional blow-moldingtechnique, the two- or three-part mold is closed and the parison orpreform is blown into the final container form in the mold. Generally,in currently utilized blow-molding techniques, the neck of the containeris associated with the portion of the mold that blows the air into themold. Further, the base of the container is associated with the portionof the mold opposite from the point where the air is blown into themold. Because of the trajectory of the air pressure into the preform,which creates the resultant container, it is generally difficult toattain the sharp corners needed to create the legs of the containeraround the recessed base; the air pressure inserted into the preformsimply cannot make the sharp corners in the legs such that the blown-outpreform completely fills the legs of mold. The top left and right ninetydegree corners of the indent which comprise the recessed base block theair pressure applied at the neck of the container from causing thepreform to stretch to this portion of the mold. Accordingly, it can bedifficult, if not impossible, with the currently utilized blow-moldingtechnologies to create the fully formed recessed base and legs shown inFIG. 3.

Further, the recessed base of these containers does not lend itself totraditional blow molding techniques with either a two or three partmold. Generally, when the mold is in the forming position (i.e., whenthe multi-part mold is closed and the parison or preform is being blowninto final container form in the mold) there is a sufficient amount ofsupport to retain the integrity of the container.

In this forming orientation, there is usually a raised step portion inthe mold which forms the corresponding recessed base in the container.Notably, when the mold is separated into its component parts to releasethe container, there is an enormous amount of pressure and mechanicalstress on the newly formed container. This is especially true for thearea of the container surrounding the raised portion of the mold at thebase. For example, although it is partially cooled in some processesafter being blown into the form, the newly formed blow-molded containergenerally has not been fully set and stabilized (e.g., it has generallynot been completely cooled into a set position and is generally stillmalleable). Stated differently, although partially cooled, the newlyformed container is still vulnerable to malformation.

It is generally impossible to create a recessed blow molded containerwith a two-part mold. As demonstrated in prior art FIG. 1, the split intwo-part molds which opens to the blow mold cavity where the hot parisonor preform is placed is generally vertical in orientation. Thus, as seenin FIG. 1, the mold opening and closing action which is necessary toclose the mold for container formation and release the formed containerafter blow-molding is a horizontal action that presses the internalportion of the vertically oriented molds together and apart. In moldswhich have a raised portion of the blow mold cavity (to create arecessed base in the formed container) the horizontal mold openingaction necessary to release the formed container from the mold cavitywould tear the base and the container apart.

The formation of recessed blow mold containers is also difficult withtraditionally utilized three-part molds. Generally, traditionallyutilized three-part molds are comprised of the same component parts of atwo-part mold, with the addition of a third part of the mold which islocated at the base of the two vertically oriented parts of the mold.Similar to the two-part mold, the cavities of the vertically orientedparts of the mold form the top, neck and side-body portions of theresultant container. The third component part of the mold, the base,forms the base of the resultant container. In order to create a recessedbase in the resultant container, the base cavity of the mold generallycontains a raised portion or step. In order to release the newly formedcontainer, the base portion of the cavity usually falls vertically fromthe container. Then, the vertically oriented portions of the containerare separated via a horizontal opening action. Alternatively, thevertically oriented portions of the container can be separated first viaa horizontal opening action followed by the dropping of the base. Oneembodiment of a three-part mold of the prior art is depicted in priorart FIG. 2.

Due to the high pressure and mechanical stress exerted on the moldbottom when the container is released, even though there is no a directconflict between the mold and recessed bottom portion of the containeras is present in a two-part mold, the recessed base of the resultantcontainer is subject to stripping and disorientation from the raisedstep and the rest of the bottom mold cavity retracting simultaneously.Due to the sensitive condition of the recently formed container, and itsfragility to malformation and disorientation at this stage, theretraction of the raised step and bottom portion of the mold at the sametime places extreme tensile pressure on the newly formed base of thecontainer, increasing the likelihood that the recessed base could becomestuck in the blow molding machine or could be unduly and improperlyaltered. The deeper this recess is, the greater the mechanical forcesapplied and therefore the increased likelihood of deformation. Thus,even with the traditional three-part mold, there is a high likelihood ofmalformation of the resultant bold molded container when a containerwith a recessed base is attempted, if the three-part mold even has theability to create a mold with a sufficiently deep foot “channel” aroundthe central indent.

SUMMARY

Because of these and other problems in the art, discussed herein areblow molding tools and a method of blow molding which provide that thetool have a retractable push up section in the base which allows for thearticle molded by the tool to have a recessed base internal to anotherwise hollow structure. As the push up is moveable, adjustment ofthe push up portion can be performed during an automated blow moldingoperation so as to allow for additional mechanical manipulation of theexpanding preform and improved release of the blow molded article.

There is described herein, among other things, a blow mold comprising: aleft half; a right half; and a base, the base further comprising apush-up portion; wherein the push-up portion of the base moves in avertical manner; and wherein the vertical movement of the push-upportion is severable from the movement of the base.

In an embodiment of the mold the push up portion is generallycylindrical.

There is also described herein, in an embodiment, a method of blowmolding for forming a container with a recessed base, the methodcomprising: providing a blow mold, the blow mold comprising: a lefthalf; a right half; and a base, the base further comprising a push-upportion; placing the blow mold in the initial open position; placing theblow mold in the closed blow molding position; blowing the preform intoa mold while simultaneously protruding the push-up portion of the baseinto the mold; and retracting the push-up portion of the base.

In an embodiment, the method further comprises returning the blow moldto the initial open position after the step of retracting.

In an embodiment of the method the protruding of the push-up portionbegins when said preform contacts said push-up portion. In analternative embodiment, the protruding of the push-up portion beginswhen said preform contacts and edge of said push-up portion.

There is also described herein a container with a recessed base formedby a process comprising the steps of: providing a blow mold, the blowmold comprising: a left half; a right half; and a base, the base furthercomprising a push-up portion; placing the blow mold in the initial openposition; placing the blow mold in the closed blow molding position;blow molding the preform into a container while protruding the push-upportion of the base; retracting the push-up portion of the base; andreturning the blow mold to the initial open position after the step ofretracting.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides a perspective view of a two-part blow molding mold ofthe prior art.

FIG. 2 provides a perspective view of a three-part blow molding mold ofthe prior art.

FIG. 3 provides a perspective view of an embodiment of a container. Thisembodiment is depicted as formed of translucent material to makeinternal structure visible.

FIG. 4 provides a perspective view of the three-part blow molding moldand the steps of the method for blow molding of the present application.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

Described herein, among other things, is a three-part mold for thecreation of blow molded containers with a base part of the mold with aretractable portion which allows for the formation of a container with arecessed base internal to an otherwise hollow structure molded by thetool. The mold generally allows for a deeper base recess to be formedthan was traditionally possible and provides that the resultantcontainer is not as vulnerable to malformation and disfigurement asrecessed-base blow molded containers formed from traditional three-partmolds without such a retractable portion or ram.

FIG. 3 provides for a perspective view of an embodiment of a container(100). The container is a general container having a relativelywide-mouth which is designed to hold a variety of goods including bulksolids (such as powders or prepared solid foods (e.g., pretzels orcookies)), liquids, and solids in liquid. Containers of this type areoften preferentially formed by blow molding as it can provide forefficient and cost effective molding as well as a desirable resultantdesign.

For ease of production by plastic molding techniques, it should berecognized that the container (100) will generally not include sharpcorners or bends but the general components will instead smoothly flowinto each other via rounded connections. While this is not required, itgenerally improves ease of manufacture. This disclosure, however, willoften refer to shapes (such as squares) that have sharp corners. This isdone purely for ease of understanding of the general orientation of theshape described. Nothing in this disclosure should be taken as arequirement that the container include perfectly flat, linear, or angledcomponents in its construction. All components may include some smoothbend without altering the basic shapes discussed.

As can be seen in FIG. 3, the center of the base (101) includes arecessed portion (103) which, in the depicted embodiment, comprises acylinder having generally vertical walls (393) and its upper end closedby a generally horizontal cap (395). The cap (395) also includes afurther depression (397) which comprises a second recessed portion intothe volume (751) of the container (100). The walls (393) will generallyconnect in a smoothly curving fashion to the base (101) generally bycurves which curve smoothly outward in a convex fashion from theinterior (751) of the container (100) into the hollow interior (399) ofthe recessed portion (103). The cap (395) will also generally connect tothe walls (393) in a smooth fashion, however, this is likely to involvea tighter concave curve providing the inside with a sharper edge.

The recessed portion (103) will generally have a diameter which isslightly larger than the diameter of the neck (109) of the container.Specifically, the diameter of the recessed portion (103) will generallybe close to, but still slightly larger than the external diameter of thelid (951) as can be best seen in FIG. 3. The height of the walls (393)will generally be similar, but slightly larger than the height of theneck (109). Specifically, the recessed portion (103) will generally havea height generally equal to the height of the neck (109) and lid (901)combination when the lid is placed on the neck in the standard fashion.

In the blow molding process of the present application which is utilizedto create recessed-base containers similar to the container depicted inFIG. 3, the process generally begins with a plastic resin hot tubecalled a parison or a preform. The parison is placed within a split moldwith a hollow cavity. The mold sides (and sometimes the bottom) are thenclamped together, thus pinching and sealing the parison tube. Air isthen blown into the tube, resulting in an expansion of the hot resinwall into the shape of the cavity. Generally, the neck of the containerneck serves as the connection between the bottle body and the source ofair which is used to inflate the container. Generally, these types ofcontainers are formed using high speed stretch blow molding techniquesas known to those of ordinary skill which provide additional strength tothe plastic which forms the container.

Because blow-molding techniques generally require that the structure tobe formed comprise a hollow balloon which is then pushed or molded intoshape, the process is particularly well suited to hollow containers asthe preform is inflated internally and pushed outward into the structureof the mold. The mold therefore is formed with an internal negative ofthe object to be formed. Thus, any recessed portions of the containerhave corresponding protrusions on the mold. This process is demonstratedin FIG. 4, which shows, step-by-step, an embodiment of the blow moldingprocess of the current application and the resultant finished bottle.

Generally, as noted previously, in order to release the finalizedcontainer traditional two-piece molds will break apart into two halveswhich are arranged vertically side-by-side. In this way, once thepreform has been formed into the mold, the two halves open which pullsthe negative internal surface of the mold from the external surface ofthe container. From this point, the container can be blown off the airsource to release it.

As should be apparent, the container of FIG. 3 cannot be ejected fromthe traditional blow mold with two halves as the recessed base portionwould serve to provide part of the mold which is in the way to theejection. Specifically, the recessed portion cannot be negatively formedon either half of the mold as the negative space inside the recessedportion is not connected to any side of the container by furthernegative space. That is, the protrusion necessary to form the basecannot be formed on either half of the mold. Doing so would result inthe mold half being inseparable from the finalized container as theportion of the recessed area that is over the mold would cause thecontainer to be transported with that half of the mold. In an extremecase, the mold attempting to release would damage the base of thecontainer.

It has been traditionally understood in the art of blow molding that anynegative recessed spaces in the container need to be formed from thesides of the container. Thus, in order to form a hollow center of thebase, two part molds traditionally provide for a relatively small centerspace with a relatively wide opening leading to it. The molds may alsobe provided in multiple pieces; i.e., in a three-part mold to createrelatively small base indents. This is the manner that a traditionalpetal-footed container was molded in the prior art, there can be acentral recesses, but that recess includes negative access spaces whichserve to create the petal shape of the base allowing access from boththe sides and the base.

The container of FIG. 3, however, does not include the negative spaceapproaching the central recess (103) and as discussed in the copendingapplication Ser. No. 13/087,883, rather it utilizes the space about thebase both to rest on a lower container's shoulder and to provide thecontainer with a solid footing. Thus, it would be undesirable todramatically increase the size of the recessed portion so as to allow itto access at least one side of the container as in a petal-footedcontainer.

Instead, the container can be formed utilizing an embodiment of the blowmold shown in FIG. 4. In the depicted blow mold (300) the mold itself(300) comprises three pieces: a base (301), a left half (303), and aright half (305). The left half (303) and right half (305) are of astandard design of a traditional blow mold tool known to those ofordinary skill in the art. As such, the left half (303) and right half(305) will provide tooling and structure for the vertical walls (393) ofthe sides of the blow molded container.

The base (301) is designed to come up from the bottom of the moldingmachine and smoothly connect with the left half (303) and right half(305) to form the depicted three-piece mold (300) in a closed position.The connection of the left half (303), right half (305) and base (301)of the molding machine from the open position to the closed position canbeen seen in step 1 (401) and step 2 (402) of FIG. 4. As seen from FIG.4, in the depicted embodiment, when in the closed position (402), theleft half (303), right half (305) and base (301) of the mold (300)generally smoothly connect together with no substantial voidsthere-between. Generally, in this closed position (402) the mold (300)generally resembles a square or cube-like structure.

The base (301) of the depicted three piece mold (300) further includes apush-up portion or ram (306). This push-up portion (306) is placedwithin a chamber of the base (301). Generally, this push-up portion(306) is a retractable mechanism, retracting and protruding in agenerally vertical manner with respect to the internal negative space ofthe mold (300). Stated differently, the push-up portion, when in theprotruded position (depicted in step 2 (402) of FIG. 4) protrudes intothe negative shape of the mold that forms the base (101) of thecontainer—the push-up portion (306) corresponds to the recessedportion(s) of the base (101) of the container. Thus, this push-upportion (306) of the mold (300) is used to form the base (101) of thecontainer and the internal recessed portion(s) of the base (101) of thecontainer.

Notably, the push-up portion (306) is generally not a rigid mold part ofthe base (301) but, instead, comprises a mold (300) element which ismoveable relative to the base (301). The vertical movement of thepush-up portion relative to the base (301) and the rest of the mold(300) in the closed position (402) is generally created by any suitablemechanical force or mechanism known to those of ordinary skill in theart including, but not limited to, cams, air or hydraulic cylinders.

In operation, the mold (300) will generally operate as follows, asdepicted in FIG. 4. In a first step (401), the left half (303), righthalf (305) and base (301) are in the initial, open position. In thisinitial, open position the mold left half (303) and right half (305) areopen, the base is down and the push-up portion (306) is down in therecessed position in the base (301). In a second step (402), the lefthalf (303), right half (305) close and the base (301) moves up (with thepush-up portion (306) in the base (301) still in the down, recessedposition) into the closed position of the mold (300). Notably, the exactorder of the pieces coming together in this second step (402) isvariable, generally any manner in which the pieces can come togetherfrom the open position (401) to the closed position (402) iscontemplated.

Once all three pieces of the mold (300) are positioned in the closedposition, the blow molding of the preform into the container will begin.Generally, any suitable method of blow molding is contemplated in thisapplication. Further, in this second step (402) the push-up (306) movesup into a protruded position simultaneously as the preform is blowmolded. This simultaneous blow molding and protrusion of the push-upportion (306) alters the forces and pressures in container formationwhich create the base (101), allowing for the clear and definedformation of the container's vertical walls (393), horizontal cap (395)and base (101). Specifically, as the air is being pushed into thepreform, the preform will generally be pushed radially out from acentralized point within the preform. In this arrangement, the base(101) will initially be formed at the center (as it is the closest pointto the air source) and the outer bottom corners of the base (101) willgenerally be the last portion of the base to form.

It should be apparent that if the moveable portion (306) was positionedin its highest (furthest into the mold cavity) position at the start ofthe blow process, the preform expansion would tend to “bridge” thechannel (307) which is used to form the foot of the container.Specifically, the material of the preform would first contact the ram(306). As it flowed out toward the channel (307), the material would bemore inclined to first flow horizontally across the channel (307)bridging the channel (307). It would then require a very large amount oftime and air pressure, to get the bridge of preform material to pushdown into the channel and assume the correct shape.

The issue is quite simple, because the air is generally applied to thepreform at an area above the center of the base in a relatively radialfashion, there is usually not enough vertical force to push the materialinto the channel (307) compared to the horizontal force to push the base(101) into the side wall.

In order to deal with this problem, the ram (306) is designed to rise asthe preform is expanding. Specifically, the push-up (306) will serve toprovide a mechanical force to the base in a vertical direction. Thisserves to force the material of the preform to flow around the corner(309) and helps to make sure that the material is pushed into thechannel (307). In effect, the ram (306) provides an additional moldingforce (in addition to the air pressure) to serve to direct the preformmaterial into the correct position and form the base (101) of thecontainer.

The exact timing of the movement of the push-up (306) compared with theblowing from air will depend on the specific size of the container, thesize and depth of the recessed portion (103) and the blow moldingtechniques being used. However, it will often be the case that thepush-up will be maintained in it lowest (or “flush”) position (403)until the preform has had material pushed close to or beyond the corner(309). IN this way, the mechanical stress serves directly to push thematerial into the channel. However, in alternative embodiments, thepush-up (306) can extend as soon as the preform material contacts thepush-up surface (311) thus providing a counter motion to the air blowmotion on the base (101) and providing for increased flow of materialover the surface (311) and into the channel (307).

After the expansion of the preform in the negative space of the mold(300) to form the container, in a third step (403) the push-up portion(306) in the base (301) will generally be retracted from the base (301)of the mold (300) to clear the recessed base of the container. As seenin step 3 (403) of FIG. 4, this retractable push-up portion (306) of thebase (301) of the mold (300) retracts from the blow molded, formedcontainer and the left half (303), right half (305) and base (301) ofthe three-part mold (300) while the three-part mold (300) is stilltogether positioned in the closed form. This reduces the mechanicalstress and high pressure which can be exerted on the feet of thecontainer that would be present in previous methods and manufacturingprocesses for blow molding.

Specifically, as the push-up (306) drops first, the inner wall (393) isreleased before the outer wall (399) of the base. This sequentialrelease provides that less force is applied to the base (101) as thebottom (301) of the mold (300) is removed. Specifically, the force ofseparation of the base (101) from the mold is separated into two stepsof reduced force, instead of a single step with significantly increasedforce. This can reduce the likelihood of mold removal causingdeformation of the container.

In a fourth step (404), once the push-up portion (306) has beenwithdrawn, the left half (303) and the right half (305) will open in thestandard fashion and the base (301) will withdraw downward, returningthe mold to the initial position, allowing the container to be ejectedin a standard fashion as is known to those of ordinary skill.

As demonstrated in FIG. 4, the push-up portion (306) will often pullaway from the container and move relative to the base (301). In otherwords, when the base (301) retracts it does so in two discreet steps.First, the push-up portion (306) retracts from the closed, moldingposition in step 3 (403). At this time, the base (301) is still up.Then, in step 4 (404), the base (301) falls down from the closed moldingposition to the initial position.

As should be apparent from the above, this two-part retraction of thebase (301) of the mold (300) frees the recessed portion of the base(101) of the container prior to freeing the rest of the base (101) ofthe container. This two-part movement thus reduces the high pressure andmechanical stress exerted on the container base (101) when the containeris released, thereby reducing the probability that the container will bestripped and/or disoriented from the raised step and the rest of thebottom mold cavity retracting simultaneously. Also, the simultaneousprotraction of the push-up portion (306) and the expansion of thepreform alters the forces utilized to create the container, making iteasier to form a container with defined legs and sharper angles at therecessed base.

In a still further embodiment, as the base (301) retracts in step 4(404), the push-up portion (306), can actually serve to push upwardsrelative to the rest of the base (301). This can serve to provide a pushto clear the container from the base (301) should the container still bein contact with the base (301) as the container is cleared from the mold(300) and, thus, can further assist in ejecting the container from themold and inhibiting deformation.

The methodology and molds discussed above provide for particularadvantage in making containers such as that shown in FIG. 3 due to thedepth and size of the recess (103) and the fact that access to therecess from the sides is generally undesirable. However, it should berecognized that a mold having a push-up portion can be used in a varietyof other container applications. In an embodiment, the push up can beused to form a container with a recess base portion (103) in a two partmold, a process that was previously impossible as the ram (306) can beretracted prior to the mold opening.

The push-up (306) can also be used to provide for decorative shapes forthe base of containers, or for the sides or tops of objects, dependingon how the object is oriented during blow molding. Specifically, thismethodology and molding mechanism may be used to form a recess, and evena very deep recess, on the portion of the object formed on the base ofthe mold. This was something that was not previously possible andtherefore often resulted in objects having to be formed in a less thanideal orientation. This need to orient to avoid a recess on the base iseliminated which can provide for additional efficiency and options inmold manufacture.

Further, while FIG. 4 contemplates only a single retractable portion(306), one of ordinary skill would understand that alternativeembodiments may utilize multiple push ups (306). This may be separate,may partially overlap, or may be nested within each other to provide forrecesses with a variety of different shapes instead of just thecylindrical recess (103) shown in FIG. 3.

While the invention has been disclosed in connection with certainpreferred embodiments, this should not be taken as a limitation to allof the provided details. Modifications and variations of the describedembodiments may be made without departing from the spirit and scope ofthe invention, and other embodiments should be understood to beencompassed in the present disclosure as would be understood by those ofordinary skill in the art.

1. A blow mold comprising: a left half; a right half; and a base, thebase further comprising a push-up portion; wherein, the blow mold has anopen position and a closed position; wherein, a preform is blown intothe blow mold in the closed position while the push-up portion of thebase simultaneously protrudes into the mold, the protruding of thepush-up portion beginning when said preform contacts an edge of saidpush-up portion.
 2. The blow mold of claim 1 wherein said push upportion is generally cylindrical.
 3. The blow mold of claim 1 whereinthe push-up portion later retracts from protruding and the blow mold isplaced in the open position after the retracting.